In performing surgical operations, use is made, inter alia, of optical fibre bundles having a small intake area into which the light of an electrical lamp system, particularly a halogen bulb and a post-positioned condenser system or of an ellipsoidal mirror lamp is beamed, for illuminating sections to be examined and operated upon by the surgeon. The ellipsoidal mirror lamp displays the highest efficiency for these purposes, but has the disadvantage that a part of the light beam is shadowed by the bulb and that consequently none but inclined light rays are incident on the end faces of the fibres of the optical fibre bundle. This has the result that the field of illumination at the egress side of the optical fibre bundle has a dark spot in the central portion which obtrudes in very disturbing manner during examination and operation in the illuminated section.
It is therefore an object of the invention to retain the favourable efficiency of ellipsoidal mirror lamps but to minimise or even eliminate the darkening of the lighting field centre, hereinabove referred to.